Sunday, October 22, 2023

Scarlet O’Honda-a CB160 revival

Several “restored” Honda bikes have come my way lately for repairs and I am reminded of the Johhny River’s lines from the tune “Secret Agent Man” that go: Beware of pretty faces that you find, a pretty face can hide an evil mind “ In this case, the pretty faces hide some unfortunate repair and assembly work, though.

So, the project of the week/weeks is a shiny red CB160 circa 1965. Sometimes known as “Chicken Hawks,” they are the 7/8s scale of the CB77 Super Hawk. They do share similar design architecture, however none of the parts interchange.

This was another of my friend Gilles’ little fleet of vintage bikes. He picked it up at a Mecum auction and had done nothing with it for a year and a half. The initial impression is that the paint quality and color seem to be right on for Honda’s Scarlet Red paint code “C.” Close-up inspections indicate a repaint rather than the original factory paintwork.

The date codes on the tires were from 2021 and 2009. These little 18” bike tires have become difficult to source in the last few years, so they indicate an older restoration. I rolled the bike onto my bike lift and started to disassemble the seat and fuel tank. The fuel lines were that awful clear plastic stuff that hardens over time and the air filters might have been originals, as they were dark and crusty-looking. The battery was a lithium battery that was totally dead. It was undersized for the battery box, so the previous owner took the battery box hardware sections and laid them on the bottom, then used a bungie cord to secure it in place.

Removing the filters and the toolbox required an SAE socket as the original metric bolts had been replaced with some cut-off threaded rod stock and matching nuts. With the filters off and away, the carburetor tops were removed, noticing that the offset carb tops for left and right side were reversed. As the slides were pulled up out of the carburetor bodies, I noticed that the slides were also reversed, so that the cutaway was facing the engine instead of the air filters. When I popped the slide needles out of the slides, the clip was all the way at the top, as the previous owner had tried to compensate for the rich fueling condition caused by backward slides.

Removing the point cover and spark advancer, the advancer weight springs were stretched which allows the weights to swing out prematurely and start unwanted spark timing advance. A little work with my duckbill pliers to crimp the spring ends did put some tension back on the weights to keep the timing under control.

The carburetors just needed a good cleaning in the ultrasound machine, plus some new float bowl gaskets. Going online just for a pair of gaskets turned out that buying a whole aftermarket kit was only slightly more expensive than just the gaskets alone. That led to a different problem as the carb kits supplied only had ISO threaded jets in #92 and #98 sizes, whereas the OEM jets are JIS thread pitch and came out of the carbs in #90 size. The supplier has been notified and confirmed that his manufacturer has made an error in packaging the jets. They intended to include both JIS and ISO jets as they are under the impression that CB160s were produced until 1969, well after the 1967 switch to ISO threaded parts.

A little research shows that the Honda ID books are showing that CB160s were “sold” from 1965-69, but that doesn’t mean that they were still in production after 1967. Honda shows the CB160s released in 07/64. The CL160s were shown as being offered from 03/66 and the CB160/CL160D kit bikes also shown in the 05/67 timeframe. Even the CA160s had an 05/66 release date. The CL160D kit bikes were electric start CB160s with CL160 body kits installed in order to move leftover bikes out of inventory. Their actual serial numbers for each year are unknown, so it is uncertain whether there were ISO bikes produced for 160 series models or not.

The 160s were replaced, first by the CL175K0 “sloper” Scrambler motorcycles (no CB175K0 bikes were sold in the US). Those were released in Jan 1968. From 1968-on, most models offered in the US had turn signals and chromed fenders, along with Candy colored paint schemes.

Honda’s Technical Service Bulletin for the change from JIS to ISO states:


In an effort to obtain more universal uniformity of threaded parts, the JIS (Japan Industrial

Standards) threaded parts standards have been modified to conform with those established by ISO

(International Standards Organization). All Japanese industry, including Honda Motor Co., is

cooperating in this change. Although the modifications of the present JIS system are not

extensive, this change will require some new tools, different tool applications, and will introduce

the possibility of non-interchangeability of similar parts.

This changeover will be effective from the start of production of all new motorcycle models

first produced after the beginning of 1967. In all other models, those previously in production, the changeover will be made gradually and on no set schedule.


Source: Honda Service Letter #74 6/8/67

The visual difference between the JIS and ISO threaded main jets is a circular groove that is machined around the outside edges of the ISO jets. JIS jets are plain on the outer surfaces, with no markings apart from the K and jet size on the faces.

The clutch lever pull was brutal and gave the impression that the clutch pack was stuck together, which isn’t unusual under the circumstances. However, in loosening up the slotted clutch adjuster locking bolt, the clutch adjuster needed to be turned quite a ways in order for the clutch lifter to contact the end of the clutch pushrod. Apparently, the early bikes used a system similar to those on the CA95 Benly, where the clutch lifter acted directly on the end of the pushrod. At some point in the 160 history, a ball bearing was added and this bike looked like it needed one. The only way to determine this is to drain the oil and remove the left dyno cover assembly so that the clutch adjuster and lifter can be inspected. It was a big surprise to discover that there was NO OIL in the engine. CB/CL160 engines actually have two drain plugs on the bottom, but neither one yielded any oil beyond a few drops. ?????

The clutch cable was an aftermarket replacement, probably for a CL160 as the fitted handlebars were higher than normal CB160 bars. The way that the cable was routed created unnecessary bends which often leads to higher-than-normal clutch pull issues. The correct routing takes the cable up from the cable joint in the left cover and over the top of the carburetors, then along the right side of the frame, where it wraps around the steering head on the way up to the handlebar brackets.

The clutch cover was removed and the condition of the plates was checked along with the correct spring sets and pushrod. The left dyno cover was removed to check for the presence of the steel ball inside the clutch lifter it was found to be in place. It is unclear why the clutch adjuster marks are 90 degrees off from where the markings are on the left case, but the clutch pull is now “normal” for the model. Honda does show two different part numbers for the clutch adjusters, so perhaps this one is incorrect for the engine.

The other odd thing was that the front axle end had an excessive amount of threads showing, as if the axle was from some other model. It has a fine thread pitch on the end with a matching axle nut. The part number for the nut is a 273 code part which is for the CL72 250 Scramblers, but the axle part number is 216 for the CB125 version of the CB160. I ordered a used axle from eBay and it came exactly as the one that was installed with the same amount of threads, showing well passed the cotter pin holes.

FYI: CB160s carried two different descriptors as Honda moved to a cc-based model number coding system. The base model for the bike is a CB125 aka a CB93, which was the evolution from the CB92 Benly Supersport. The CB160 version of the bike also carried a CB96 moniker. The spark advancer was stamped CB93 for instance. People can become confused with the CB93 sounding like the CR93 Factory race bike series. In truth, there is a lot of CR93 architecture shared with the CB125/160 models. A number of the part numbers on the 160s are 222 codes which were for the CR93. Interestingly, the frame section beneath the fuel tank has two sets of mounts for the ignition coil. The CB125/160 only used the single double-ended coil due to the 360-degree firing crankshaft, but the CR93 had dual coils because of the dual ignition points and the 180-degree firing crankshaft design.

A new standard lead-acid battery was procured and charged. The battery tray was re-installed correctly to allow for the full-sized battery to be placed back in the chassis in the original configuration.

More difficulties were encountered by the aftermarket throttle cable, which was excessively long and created routing problems of its own. Ordering cables online can be a challenge as sellers often just show the appropriate Honda part number, but don’t offer the dimensions to verify that it may or may not fit a specific application. Because of the odd handlebar reach, I wound up using a CB77 low-rise handlebar throttle cable from Tim McDowell’s site. Every cable that was supposed to be fitting 160 or 175/200 models all had throttle ends that were too short for the 160 carb slides.

After a normal tune-up sequence, the bike fired up sounding normal, especially after I reinstalled the stock baffles that had come in a box of spares with the bike. A brief check ride around the neighborhood and down the long grade towards the Bonita post office gave a good feeling about the bike, including a nice light clutch pull. Now it is back to its owner for his enjoyment, as Fall approaches here in SoCal.

Bill Silver

aka MrHonda